Rik privately asked for some images of this in effect. Try this
Chromium bug: http://code.google.com/p/chromium/issues/detail?id=152304
The "before" pic shows grayscale anti-aliasing, the "after" pic shows
LCD anti-aliasing, both on Mac. It should be pretty obvious that
switching between the two as opacity transitions from .99 to 1 would
be undesirable.
~TJ